The present technique relates to a drive device of a light emitting element that emits light with luminance depending on a flowing current, such as a light emitting diode (LED), a light emitting element drive method, and a display apparatus that uses the drive device and the drive method and has e.g. a non-luminous, transmissive display section.
For the backlight of a liquid crystal panel, a light emitting diode (LED) is used as the light source to replace the cold cathode fluorescent lamp (CCFL) type using a fluorescent tube.
In particular, a method of individually using the respective primary colors of red LED, green LED, and blue LED and optically performing synthetic additive color mixing to obtain white is used for television use because it easily provides favorable balance of the colors. In recent years, improvement in the color rendition of the white LED is advanced and it is coming to be frequently used for television use.
The LED has a characteristic that the luminance changes depending on the current basically, and the forward voltage varies depending on variation in the individual difference and the temperature.
Therefore, when the LED is used as the backlight of a liquid crystal panel (e.g., a liquid crystal display (LCD)), a drive device therefor is required to have the constant current characteristic to obtain certain uniform luminance.
The following drive device is known. Specifically, this drive device employs a pulse width modulation (PWM) control system in which the current flowing to an LED is turned on/off at certain timing and the luminance is adjusted based on the ratio of its on/off-period in order to stably adjust the luminance in a wide dynamic range.
As one of methods to realize this system, a method in which a switch element is inserted in series to the LED and is turned on/off at certain set timing is employed (refer to e.g. Japanese Patent Laid-open No. 2001-272938).
A system is also known in which a switch element connected in series to an LED is turned on/off by a lighting signal and PWM control of a switching transistor in a switching power supply section of e.g. a boost chopper type is carried out.
In a LCD monitor, normally control like that shown in FIG. 1 is carried out in order to suppress the influence of image lag (crosstalk) that occurs because of the low response speed of the liquid crystal at the time of image switching.
Specifically, in the LCD monitor, the on/off-timing of the backlight is controlled in association with the image switching to thereby keep display of clear images.
The on/off-timing of the backlight in this control is as follows. In a crosstalk period, the backlight is turned off as black insertion. Only in a period when crosstalk occurs as hardly as possible, the backlight is turned on to display images.
However, in this case, there is an adverse effect that the luminance of the whole backlight decreases. In order to prevent this, surging the amount of drive current (peak current amount increase) is performed to keep the brightness of images.